Dry-kiln



(No Model.)

A. S. NICHOLS. DRY K'ILN.`

Nq.553,928. rammed Feb. 4, 1896.

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WITNESSES.'

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UNTTED STATES PATENT OFFICE.

AARON SAVYER 'NICI'IOLS, OF CHICAGO, ILLINOIS, ASSIGNOR TO HIMSELF, AND GEORGE B. HOWARD, OF BROOKLYN, NEI/V YORK.

DRY-KILN.

SPECIFICATION forming part of Letters Patent No. 553,928, dated February 4, 1896.

Application filed December Z4, 1894. Serial No. 532,763. (No model.)

T0 all wiz/0m t may concern:

Be it known that I, AARON SAWYER Nien- OLs, a citizen of the United States, residing in Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in the Construction of Dry-Kilns and the Method of Operating Them, of which the following is a specification.

This invention rela-tes to the construction of dry-kilns and the'method of operating them, and has been devised specially for use with that class of driers consisting of a series of platens each provided with a coil of heatingpipe and placed one above another in a pile with a thickness of lumber between each adjacent pair of platens. Driers of this character are most advantageously placed in a suitable sized compartment adapted to be entirely closed, so as to confine the moisture given off by the lumber or supplied from the steam-pipes, and thereby keep the lumber in a moist atmosphere during a portion at least of the operation.

The first feature of my invention has for its object the provision of improved means for Ventilating the dry house or compartment containing a drier composed of individuallyheated platens, to the end that the work done maybe Jfacilitated and improved in character.

The second feature relates to a new method of operating such a kiln whereby I avoid all checking in the lumber operated upon and secure its perfect and thorough drying.

The nature of my invention is fully stated in subsequent parts of this specification, and such features thereof as relate to construction are shown in the accompanying drawing, wherein is given a vertical section of the driercompartment, the drier being shown in elevation.

In said drawing, A A represent the series of platens forming the drier proper,'and B B are a portion of the pipes by which steam is fed to the coils in the interior of the platen.

C C are the usual hydraulic jacks used with the platens.

D is the dry-house surrounding the drier. It is provided with air-inlet pipes E, which are preferably of metal and located wholly within the room. The usual method of admitting cold air through openings located at the top of the room I find to be a failure, as the hot air will go out of such openings instead of allowing cold air to come in, thereby creating a waste of heat as well as a loss of moisture. My inlet-pipes .E draw the outside air from a level near that of the floor I and deliver it inside the room near the top thereof, which prevents the escape of either heat or moisture through these pipes. Being thus located the warmth in the room raises the temperature of the pipes above that of the air drawn in by them and thus stimulates the draft through them. i The dry-room is also provided with a suitable number of air-eX- haust pipes F, preferably of metal. These take the air from the bottom or near the iioor of the drying-room and discharge it above the roof, where they are supplied with suitable cowls or hoods G adapted to prevent downcurrents and the entrance of snow and rain, and also adapted to increase the upward movement of the air.

No radiators or steam-pipes are needed in the drying-room if it is suitably constructed for the drier, all the heat necessary being obtained from the platens themselves.

I make no provision in the dry room or house for the condensation of the moisture, but retain all the moisture driven out of the stock in the surrounding atmosphere during the first stage of the operation.

Suitable valves H are employed in all the air-pipes E and F, and such valves are preferably provided with operating devices eX- tending to the outside, so that all can be closed or opened at different stages in the operation without opening the kiln-room.

Vith this apparatus and house the mode of operation is as follows: The lumber having been placed between the platens in the usual manner and the latter lowered so as to bear upon both sides of it, the steam is then turned into the platens,which,becoming heated, soon act upon the wood. This immediate contact of the heated platens with both sides of every board converts the moisture therein into vapor and it rises, as is natural with heated air, to the top of the room. I also close all the air-valves H and thus prevent both the entrance of the fresh cold air as well as the escape of such moisture as may be in the room,

IOO

and thus produce a condition of hot moist air in the room, which condition is maintained until it is certain that the central or inner portions of the stock have become thoroughly heated through.

I nd that it is very essential that the out side of the lumber be kept moist and thus prevented from drying until the inner portions have become thoroughly heated, because when the outside is allowed to dry prematurely it seems to crust over the outside of the lumber and to seal up within it what moisture may then remain therein, and the more dry heat is applied the more difficult it becomes to extract this remaining moisture, as the outside continues to dry and shell over, finally becoming casediardened. This is the cause of honeycombing or interior checking. The length of time the stock is thus maintained in the wet atmosphere depends upon the size of stock and kind of wood, thicker stock requiring more than thin and some woods needing more than others.

XVhen the stock has become thoroughly heated through with hot moist air, the valves v in the pipes E and F are gradually opened to suit whatever stock is being dried until finally the air is given t'ree circulation.

The heat of the platens, being continued throughout the operation, acts to draw the moisture from the center ot the stock both ways to the surfaces, and thence it rises to the top of the room. Upon opening the valves II the fresh air is also admitted to the upper part of the room through the pipes E and there mingles with the heated and moist air arising from the stock, and being the cooler it chills the latter, so that both fall to the floor, where the upward suction in pipes F draws them out of the room.

As long as there is moisture in the wood there must be moisture in the room. Hence the first stage of the operation is carried on in a moist atmosphere. The circulation referred to is continued until all the moisture in the stock has been drawn out and the suri face of the lumber dried off. lt is wholly a natural circulation and needs no attention from attendants beyond the opening and clos t ing oi' the valves. The heat is also continued in the platens until the lumber is thoroughly i dry.

l lt will be noticed thatby my improved pro- 1 cess and apparatus the heat is applied directly to the lumber by the platens of the drier, and that the chamber ot' the kiln is warmed by the heat derived from the same platens. lt results from this that the lumber is subjected to a high heat and the temperature which prevails in the chamber outside l ot the platens, While it may be less than that I which the lumber receives directly from the platens, is yet sufficiently high to prevent condensation of the pervading moisture. The l atmosphere thus becomes surcharged with l the vapor and the surface of the wood so sofl tened that the esca-pe of the moisture from i its interior is facilitated, and by maintaining the heat in the platens and this moist and hot condition ot the air until the interior parts of the wood have become thoroughly heated I effectually drive out all confined moisture from the wood and prevent case-hardening. I l am also enabled to greatly quicken the dryi ing` operation.

l l claiml The improved dry kiln or room consisting of a chamber, the walls whereof are adapted to prevent condensation of the moisture within it, an air-inlet and an air-outlet pipes lo cated within the chamber and each provided with a valve whereby it may be closed, the inlet-pipes drawin gin the outside air and discharging it near the top of the chamber, and the outletpipes drawing the inside air from the floor ot' the chamber and discharging it 1 above the top thereof, and means for stimulating the draft through said outlet-pipes, in combination with a series of individually heated platens adapted to receive the lumber between them and exert heat thereon, and also adapted to warm the air Within the chamber, substantially as specified.

AARON SAXVYER NICHOLS.

Yi'itnesses:

FRED M. PURMORT, lino. W. DooNE, Jr. 

